结合波束形成与发射分集的闭环下行发射方案

多天线技术是提高下行发射性能的一种有效方法。波束形成(BF)和发射分集(TD)均通过使用多个天线来有效地改善系统性能并提高信道容量。该文提出了一种将BF和TD结合用于闭环通信系统的自适应下行发射方案, 它包括适合于慢变信道的分集阵列方法和适合于快变信道的波束形成阵列方法。基站可以根据实际的信道状况自适应地调整发射方法。文中详细地介绍了自适应方案的实现算法,并对算法的复杂度和适应环境进行了分析。仿真结果证明新方案可以同时获得BF增益和TD增益,在使系统的误比特率(BER)性能大幅提高的同时,增强了系统对信道变化的适应能力。

A Scheme of Joint Beam-Forming and Transmit Diversity for Closed-Loop Downlink Transmission

Multi-antenna technique is an effective means of improving performance of the downlink transmission. Both Beam-Forming (BF) and Transmit Diversity (TD) which exploit multiple antennas are attractive candidates for improving the system performance and increasing the channel capacity. In this paper, an adaptive downlink transmission scheme combining BF with TD in the closed-loop mode is proposed. And it includes two methods, one uses the diversity antenna array and is suitable for the slowly time-varying channel, and the other uses the BF antenna array and is suitable for fast time-varying channel. The transmitter can adaptively change the transmission mode between two methods according to the actual channel States. The algorithm of the adaptive scheme is investigated in the paper, and the complexity of the algorithm and its applicable environment are also analyzed. The simulation results show that the new scheme can achieve both BF gains and TD gains; while it improves the performance of the Bit Error Rate (BER), it can enhance the adaptive ability to the channel variance of the wireless system.